Project Summary Failure of pancreatic ? cells underlies the progression of all forms of diabetes. ? cells are uniquely susceptible to stress induced cell death due to the high demand of insulin biosynthesis and secretion and to oxidative stresses resulting from well-documented low antioxidant enzyme activity. Pancreatic and duodenal homeobox 1 (PDX1) is a human diabetes gene and transcription factor that is required for ? cell function and survival during islet compensation for diet induced insulin resistance. We find Pdx1 in complex with Activating Transcription Factors (ATFs) which are well known to coordinate cellular stress responses. We hypothesize that PDX1, ATF4, and ATF5 form a stress responsive transcriptional regulatory complex that directs ? cell fate under stress conditions. This will be tested in three Specific Aims: 1. Characterize the stress-induced PDX1 transcriptional complex, 2. Identify the transcriptional targets of the stress-induced PDX1 transcriptional complex, and 3. Elucidate the functional roles of PDX1 targets in ? cell survival. We will employ cutting edge proteomic techniques to identify the components of the stress- induced PDX1 transcriptional complex and any associated post-translational modifications. Further, we will integrate ChIPExo and RNASeq profiles of mouse and human ? cells under physiologically and pathophysiologically relevant stress to obtain a comprehensive genome wide identification of the transcriptional targets of this complex, leveraging the near base pair resolution of ChIP-Exo to resolve structurally distinct modes of transcription factor binding, thereby enabling new insights into stress responsive gene regulation in the beta cell. Finally, we will pursue the functional role of the Pdx1-Atf4-Atf5 target Gpt2 in primary mouse and human islets to test the hypothesis that the beta cell is metabolically reprogrammed by fuel excess in a manner analogous to what occurs during transformation of cancer cells. Together these results will describe new gene targets that regulate the cell fate decisions important for ? cell survival in response to diabetes related stresses, and expand the translational applications for human diabetes of the PDX1 stress responsive transcriptional complex.